This section provides background information related to the present disclosure which is not necessarily prior art.
Vibration dampers are commonly used with rotating shafts or other rotary components in a power transmission system, such as a crankshaft of an internal combustion engine. The purpose of such vibration dampers is to damp the torsional vibrations at a specific frequency that is associated with the vibrations caused by the cyclic forces applied to the rotary components during rotation.
In automotive vehicles that transmit rotary power from a powertrain to a rear axle via a propshaft, it is possible for the propshaft to transmit vibration at a first frequency to the rear axle (from the powertrain) and to transmit vibration at a second, different frequency to the powertrain (from the rear axle). It was relatively commonplace to alter the operational characteristics of the powertrain (e.g., the torque converter or the transmission) to attenuate vibrations transmitted from the powertrain to the propshaft, as well as to employ a vibration damper to dampen vibrations transmitted from the rear axle to the propshaft. As such alterations to the operational characteristics of the powertrain can adversely affect the mileage of a vehicle, there is increasing resistance on the part of original equipment manufacturers to make such alterations. Consequently, it is increasingly necessary for designers of vehicle drivelines to deal with multiple sources of vibration in the vehicle driveline.
One approach that we have considered includes the use of a first vibration damper that is coupled to a first side of the vehicle propshaft for attenuating vibration at the first frequency, and a second vibration damper that is coupled to a second side of the vehicle propshaft for attenuating vibration at the second frequency. While such solution can be effective in some situations, we noted that there is considerable cost associated with the provision and installation of two discrete vibration dampers. Moreover, it would not be possible in some situations to integrate two discrete dampers into the vehicle driveline.